Carlos Garza is a regular contributor to Pro Audio Review.
Aphex Systems, celebrating 26 years in the pro audio industry, has unleashed a revitalized version of its famous Aural Exciter. The Model 204 Aural Exciter with Optical Big Bottom is a big name for this single rack-space box that packs a lot of flexibility into an affordable package.
Product Points
Applications: Studio, restoration, broadcast, multimedia, live sound, contracting/install.
Key Features: XLR and 1/4-inch TRS I/O (+4 and -10); independent channel controls; independent control of Aural Exciter and Big Bottom processing.
Engineers are constantly dealing with customers who want the loudest mix. "It has to go to 11 and have a big bottom." Aphex was obviously listening and came up with a pair of effects that create the impression of a cleaner, louder mix without dangerous side effects.
Features
What's new in this update on the original Model 104? The 204 adds frequency and dynamic control of low-end response, a revamped front panel and an internal power supply. The new millennium shiny finish and slightly textured knobs add a bit of sex appeal.
The rear panel has a pair of operating level switches allowing independent selection between -10dBV and +4dBu. Inputs and outputs now include XLR connectors in addition to the 1/4-inch TRS found on the older model. Both inputs accept unbalanced inputs as well.
The manual is loaded with useful information on cable wiring and avoidance of ground loops. This includes diagrams for "pseudo-balanced" wiring of unbalanced equipment (for example, 1/4-inch TS to XLR).
The Model 204 also has separate controls for the Aural Exciter and Big Bottom. This means that you can use one channel as a low-end enhancer and the other as a high-end enhancer and bus each channel into separate effects sends on your console.
The Aural Exciter and the Big Bottom sections each have a tuning knob that lets you select the range of frequencies for processing. You have to refer to the manual if you want to know exactly which frequencies you are selecting. A continuously variable knob is used to select the amount of harmonics added by the Aural Exciter.
The Tune control for the Aural Exciter sets the corner frequency for the high-pass filter. The lowest setting enhances frequencies from 800 Hz on up. Turning it completely clockwise means that you are only enhancing frequencies above 6.1 kHz. Likewise, the Tune control for the Big Bottom sets the highest frequency for bass enhancement (from 49 to 197 Hz).
The big story is the Optical Big Bottom circuit. This new circuit features a Light Dependent Resistor (LDR) that allows coupling of a controllable light source to a variable resistor. After passing the signal through the low-pass filter, the signal is fed through the adjustable drive circuit, which feeds the LDR.
In principle, the LDR reacts immediately to the bass signal but fades slowly like a long release on a compressor. If you have the drive knob set correctly, you should hear more sustain from only the loudest notes. This is designed to produce a dynamic and resonant bass without a big increase in peak level or overall low-frequency content.
In Use
I set out to restore some 1980s-era garage band recordings that originated on 1/2-inch 8-track and were mixed to 1/4-inch 2-track. I transferred the tracks into Pro Tools at Pepperland Recording and attached the Model 204 to the Digidesign 888 I/O using the balanced XLR connections. I created an effects loop using channel sends and an auxiliary bus for the return.
On some tracks, I wanted to bring out the vocal so I dialed in the lowest frequency on the Aural Exciter tuner. In cases where the vocal presence was fine, I went for enhancement of higher frequencies with the single goal of getting more "air."
The manual says the 204 can "restore presence and clarity, improving transient response of individual tracks or the whole mix." The 204 did not disappoint in this regard. Some of the tracks suffered from a distant and muted-sounding snare drum. The Aural Exciter made the attack transients brighter and sharper.
Of course, it will not fix a bad mix, but it can help produce a cleaner overall sound. When bypassed, I felt like I had to work to hear all of the instruments. With the effect in, I had no trouble hearing each part. The whole mix was present, wider and felt more balanced. Every instrument seemed to sit more consistently in its own space. The guitar had more bite, the keyboards were shimmering, the vocal was present and the words more intelligible.
One important aspect of the Aural Exciter and the Big Bottom is that the effects are more perceptual than physical. It sounds like there is a lot more bass and high end than is present on the signal meters. I found myself using less EQ in general.
The Model 204 can also be used to preprocess tracks for low-quality playback. Listeners can be fooled into not missing the high frequencies that are lost in typical MP3 and cassette recordings if the high end that they do hear is enhanced.
Some of my customers ask me to prepare backing tracks for dance and vocal competition. The final product, which goes out on cassette, has to sound clear and big. I found that the Big Bottom added a lively punch on most mixes.
Some of these sessions are rush jobs and it is nice to be able to quickly see the when the input signal is being processed by the Big Bottom. I started with the tune knobs set at 12 o'clock and drive knobs turned all the way down. I then raised the drive slowly until the LED showed that the effect was active on most of the bass hits. Then I adjusted the Big Bottom tune knob to focus in on the kick drum.
The result was more interesting than just adding low end EQ. The louder notes seemed to hang a bit more than the quiet notes. The intelligent transient sensitivity also made a muffled kick drum on one track sound crisp and clear. The effect was like changing a soft beater to a wooden beater. This is a very musically useful effect.
I only had a few quibbles with the 204: I would like to see the frequencies labeled on the front panel for the tuning knobs. I can imagine, in a mixing situation, dialing in frequencies on a shelving EQ and wanting to adjust appropriate frequencies in the Aural Exciter.
I also wish there was more control of the Big Bottom effect. Specifically, a release control for the low-end enhancer would really help tailor the effect to the tune/tempo.
Summary
I have had several studio customers that wanted to digitize and "restore" old recordings. Remember that a processor like this will not put back something that has been lost. When an analog tape has lost its high end, it is usually gone for good. However, the Model 204 can bring a lot of life to a dull sounding track.
The harmonics that it constructs are useful and musical. You hear each part with more clarity and presence. At a suggested retail price of $400, the new Aphex 204 is a useful addition to any studio rack or live sound rig.
REVIEW SETUP
TASCAM DA-30 DAT; Digidesign Pro Tools; Mackie 1402 mixer (for monitor switching); Alesis RA-100 power amplifer; Tannoy PBM 8 studio monitors, Altec Lansing multimedia speakers; TASCAM 122 mkII cassette deck.
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